Microwave oven



Jan. 19, 1965 K. FRITZ 3,166,663

MICROWAVE OVEN Filed July 15. 1960 INVEN TOR KARL FRITZ KENWAY, JENNEY,WlTTER & H|LDRETH ATTORNEYS 3,166,663 MICROWAVE OVEN Karl Fritz,Freiburg, Breisgau, Germany, assignor to Miwag Miirrnwellen'AG., Basel,Switzerland, a corporation of Switzerland Fiied July 13, 1W0, Ser. No.42,631

11 Claims. (Ci. 219-1035) This invention relates to microwave ovens,particularly to those of the tunnel type employed for continuousoperation. In general, the invention provides continuous sealing of thetreating chamber against the escape of microwave energy.

Microwave ovens are commonly used for various types of treatments, suchas heating, with microwave energy. In one known type the objects to betreated are advanced continuously through the oven by means of aconveyor belt, conveyor chain, or rollers, but in them microwave energyis lost unless means are provided to seal the inlet and outletpassageways. For this purpose sealing gates of various types have beenemployed to form a lock which effects a continuous closure of the entryand exit passageways. The operation of these gates requires aninterruption of the motion of the objects to be treated it loss ofenergy under continuous operation of the microwave generator is to beprevented.

The present invention provides continuous sealing of the oven againstthe escape of microwave energy by means of a conveyor having a pluralityof spaced panels which are arranged to extend across the entrypassageway and exit passageway to provide a continuous closure of thesepassageways while being advanced through them. Within the oven, thepanels serve to carry the objects to be treated and expose them to thesource of microwave energy.

In a preferred embodiment of this invention, the oven forms a horizontalchamber which communicates with a source of microwave energy in aconventional manner. Entry and exit conduits extend vertically from theends of the oven and the conveyor thus runs down through the entryconduit, horizontally through the tunnel and upwardly through the exitconduit. The panels are carried by the conveyor in a constantlyhorizontal position, and thus serve to block the entry conduit and theexit conduit from the escape of microwave energy during their passagethrough the conduits. In the horizontal chamber the panels are parallelto the length of the chamber and cause the objects carried by them to beexposed to the radiation.

The conveyor panels are preferably formed with edge walls each having anannular groove, which in conjunction with the walls of the entry andexit conduits, forms a conventional quarter-wave chamber having highimpedance. An over-all effective seal is thereby maintained even whendirect electrical contact between the panels and the walls of the entryand exit conduits is not made. A further preferred feature of amicrowave oven of this invention is a spacing of the panels in the entryand exit conduits such that the chamber formed between them does notexhibit cavity resonance. These features will obviously depend upon theparticular frequency employed, from which the proper dimensions can *becalculated by well known procedures.

This invention is described in detail below with reference to theaccompanying drawing, in which a sectional elevation of the presentlypreferred embodiment is shown schematically.

In the embodiment illustrated, the microwave oven is embodiedprincipally in a horizontal tunnel 1, having typically a rectangularcross section. Microwave energy is supplied to the oven from a generator2 through a wave guide 3 and slots 4 formed in the upper wall of theoven United States Patent "ice 1. An entry conduit 5 and an exit conduit6 extend vertically from the ends of the tunnel, and through these arecarried a plurality of spaced panels 7, of metal or other electricallyconductive material, which constitute a conveyor by which objects to betreated are carried into, through, and out of the oven. The panels 7 aretypically carried between chains 10 (only one being shown) supported onsuitable sprockets and driven by conventional means (not shown). Thepanels 7 are connected between the chains 10 in a manner such that thepanels always hang in a horizontal position and substantially completelyblock the entry conduit 5 and the exit conduit 6. The chains run besidethe panels, conveniently in groves provided in opposite side walls ofthe entry and exit conduits 5 and 6 where the space they occupy isconstantly closed to the escape of microwave energy.

Most effective sealing by means of the panels 7 is provided by formingtheir edges 8 with an inwardly extending annular groove 9 to formquarter-wave trap. The panels thus assume a form of a metallic box, openat its bottom and having side walls provided with annular indentationsone-quarter wave length deep.

From the foregoing description it will be seen that objects carried bythe panel 7 are exposed within the tunnel 1 to the microwave energysupplied through the slots 4. The panels further serve while bringingthe objects into the tunnel through the entry conduit 5 and whilebringing the object's out of them through the exit conduit 6, to providea seal against the escape of microwave energy by blocking theseconduits. For this purpose the conduits are at least as long as thespace between the panels so that at least one is always present withineach conduit.

Although this invention has been described with reference to itspreferred embodiment, it is contemplated that obvious modifications willoccur to those skilled in the art and that such modifications may bemade without departing from the scope of this invention. In particular,it is noted that microwave ovens, including the means by which they aresupplied with microwave energy, and also numerous types of conveyorsystems are well known to the art and any of numerous conventional typesmay obviously be employed in the practice of this invention.

Having thus disclosed my invention and described in detail a preferredembodiment thereof, I claim and desire to secure by Letters Patent:

1. Apparatus for treating objects with microwave energy comprising ahorizontal treating chamber, a source of microwave energy communicatingwith said chamber, a Vertical entry conduit leading to said chamber, avertical exit conduit leading from said chamber, and conveyor means forleading objects to be treated through said entry conduit, chamber, andexit conduit, said conveyor including a plurality of spaced horizontalpanels for supporting objects to be treated in exposure to said source,said panels being carried horizontally to extend across said entryconduit and exit conduit during their passages therethrough and providea seal therein preventing the escape of microwave energy from saidchamber.

2. Apparatus for treating objects with microwave energy comprising ahorizontally-extending treating chamber, a source of microwave energycommunicating with said chamber, a vertically-extending entry conduitleading to said chamber, a vertically-extending exit conduit leadingfrom said chamber, and conveyor means for leading objects to be treatedthrough said entry conduit, chamber, and exit conduit, said conveyorincluding a plurality of spaced panels for supporting objects to betreated in exposure to said source, said panels being arranged to 3extend across said entry conduit and exit conduit during their passagestherethrough and each having edge walls formed with an annular grooveforming with the walls of said entry conduit and exit conduit aquarter-wave trap, thereby providing a seal within said conduitspreventing the escape of microwave energy from said chamber.

3. Apparatus for treating objects with microwave energy comprising ahorizontally-extending treating chamber, a source of microwave energycommunicating with said chamber, a vertically-extending entry conduitleading to said chamber, a vertically-extending exit conduit leadingfrom said chamber, and conveyor means for leading objects to be treatedthrough said entry conduit, chamber, and exit conduit, said conveyorincluding a plurality of spaced panels for supporting objects to betreated in exposure to said source, said panels being arranged to extendacross said entry conduit and exit conduit during their passagestherethrough and said conduits being longer than the space between saidpanels whereby said panels form a seal within said conduits preventingthe escape of microwave energy from said chamber.

4. Apparatus for treating objects with microwave energy comprising ahorizontally-extending treating chamber, a source of microwave energycommunicating with said chamber, a vertically-extending entry conduitleading to said chamber, a. vertically-extending exit conduit leadingfrom said chamber, and conveyor means for leading objects to be treatedthrough said entry conduit, chamber, and exit conduit, said conveyorincluding a plurality of spaced panels for supporting objects to betreated in exposure to said source, said conduits being longer than thespace between said panels, and said panels being arranged to extendacross said conduits during their passages therethrough and each havingedge walls formed with an annular groove forming with the walls of saidconduits a quarter-wave trap, whereby a seal with said conduits isprovided.

5. Apparatus as defined by claim 3 wherein the panels are spaced apartan amount forming an aresonant cavity between the panels within theentry and exit conduits.

6. Apparatus as defined by claim 4 wherein the panels are spaced apartan amount forming an aresonant cavity between the panels within theentry and exit conduits.

7. Apparatus for treating objects with microwave energy comprising ahorizontal treating chamber, a source of microwave energy communicatingwith said chamber, a verticfl entry conduit leading to said chamber, avertical exit conduit leading from said chamber, and conveyor means forleading objects to be treated through said entry conduit, chamber, andexit conduit, said conveyor including a plurality of spaced horizontalpanels for supporting objects to be treated in exposure to said source,said panels being carried horizontally to extend across said entryconduit and exit conduit during their passages there'- through and eachhaving edge walls formed with an annular groove forming with the wallsof said entry conduit and exit conduit a quarter-wave trap, therebyproviding a seal within said conduits. preventing the escape ofmicrowave energy from said chamber.

8. Apparatus for treating objects with microwave energy comprising ahorizontal treating chamber, a source of microwave energy communicatingwith said chamber, a vertical entry conduit leading to said chamher, avertical exit conduit leading from said chamber, and conveyor means forleading objects to be treated through said entry conduit, chamber, andexit conduit, said conveyor including a plurality of spaced horizontalpanels for supporting objects to be treated in exposure to said source,said panels being carried horizontally to extend across said entryconduit and exit conduit during their passages therethrough, and saidconduits being longer than the space between said panels whereby saidpanels form a seal within said conduit-s preventing the escape ofmicrowave energy from said chamber.

9. Apparatus for treating objects with microwave energy comprising ahorizontal chamber, a source of microwave energy communicating with saidchamber, a vertical entry conduit leading to said chamber, a verticalexit conduit leading from said chamber, and conveyor means for leadingobjects to be treated through said entry conduit, chamber, and exitconduit, said conveyor including a plurality of spaced horizontal panelsfor supporting objects to be treated in exposure to said source, saidconduits being longer than the space betweensaid panels, and said panelsbeing carried horizontally to extend across said conduits duringtheirpassages therethrough and each having edge Walls formed with an annulargroove forming with the walls of said conduits a quarter-wave trap,whereby a seal with said conduits is provided.

10. Apparatus as defined by claim 8 wherein the panels are spaced apartan amount forming an aresonant cavity between the panels within theentry and exit conduits.

11. Apparatus as defined by claim 9 wherein the panels are spaced apartan amount forming an aresonant cavity between the panels within theentry and exit conduits.

References Cited the file of this patent UNITED STATES PATENTS 2,467,230Revercomb et al Apr. 12, 1949 2,868,939 Pound Jan. 13, 1959 FOREIGNPATENTS 1,260,933 France Apr. 196i

1. APPARATUS FOR TREATING OBJECTS WITH MICROWAVE ENERGY COMPRISING AHORIZONTAL TREATING CHAMBER, A SOURCE OF MICROWAVE ENERGY COMMUNICATINGWITH SAID CHAMBER, A VERTICAL ENTRY CONDUIT LEADING TO SAID CHAMBER, AVERTICAL EXIT CONDUIT LEADING FROM SAID CHAMBER, AND CONVEYOR MEANS FORLEADING OBJECTS TO BE TREATED THROUGH SAID ENTRY CONDUIT, CHAMBER, ANDEXIT CONDUIT, SAID CONVEYOR INCLUDING A PLURALITY OF SPACED HORIZONTALPANELS FOR SUPPORTING OBJECTS TO BE TREATED IN EXPOSURE TO SAID SOURCE,SAID PANELS BEING CARRIED HORIZONTALLY TO EXTEND ACROSS SAID ENTRYCONDUIT AND EXIT CONDUIT DURING THEIR PASSAGES THERETHROUGH AND PROVIDEA SEAL THEREIN PREVENTING THE ESCAPE OF MICROWAVE ENERGY FROM SAIDCHAMBER.